1. Technical Field
The present invention relates to a tubular transfer system for a drill rig, and in particular, to a tubular transfer system that moves the tubulars between a horizontal position on the deck and a vertical position at the rig floor entry.
2. Description of Related Art
Drill rigs have utilized several methods for transferring tubular members from a pipe rack adjacent to the drill floor to a mousehole in the drill floor or the well bore for connection to a previously transferred tubular or tubular string. The term xe2x80x9ctubularxe2x80x9d as used herein includes all forms of drill pipe, drill collars, casing, liner, bottom hole assemblies (BHA), and other types of tubulars known in the art. Conventionally, drill rigs have utilized a combination of the rig cranes and the traveling system for transferring a tubular from the pipe rack to a vertical position above the center of the well. The obvious disadvantage with the prior art systems is that there is a significant manual involvement in attaching the pipe elevators to the tubular and moving the pipe from the pipe rack to the rotary table. This manual transfer operation in the vicinity of workers is potentially dangerous and has caused numerous injuries in drilling operations. Further, the hoisting system may allow the tubular to come into contact with the catwalk or other portions of the rig as the tubular is transferred from the pipe rack to the drill floor. This can cause damage to the tubular and may affect the integrity of the connections between successive tubulars in the well. Finally, past systems have only been able to transfer single joints of pipe or casing.
In response to the disadvantages of a conventional handling system, other prior art apparatuses for gripping a drill pipe and transferring the pipe from a horizontal position on the pipe rack to a vertical position above the drill floor have been developed. Some of these systems allow the pipe to be handled without the necessity of manual interaction in grasping the pipe or transferring the pipe to the well. One of these apparatuses is disclosed in U.S. Pat. No. 3,633,771 to Woolslayer, et al. Woolslayer teaches a drill string that is moved by a strongback having hydraulic grasping jaws. This apparatus is mounted to the drilling platform and is centered in the V-door of the rig.
Another apparatus is disclosed in U.S. Pat. No. 4,834,604 to Brittian et al. Brittian teaches a strongback that is connected to a one piece boom with the boom being mounted on a base located adjacent the rig and operating directly through the V-door of the rig. The strongback transfers pipe through the V-door to a vertical position and raises or lowers the pipe so that a connection between the pipe and the drill string can occur.
Yet another apparatus is disclosed in U.S. Pat. No. 5,458,454 to Sorokan. Sorokan discloses a pipe handling method for moving tubulars from a horizontal position on a pipe rack adjacent to the well bore to a vertical position over the center of the well by using a bicep and forearm assembly and gripper head for attachment to a tubular. The tubular is moved along or close to the conventional path of the tubular utilizing known cable transfer techniques so as to allow access to the drill floor through the V-door of the rig. More recent designs have utilized a deck transfer system complete with a conveyer to move individual joints from the deck area to the rig floor entry.
The disadvantages of the prior art are several: a substantial amount of human physical contact with tubulars and lifting devices is required; the process for transferring tubulars is lengthy, costing more in rig time and total operational spread cost; the condition of a drilled hole deteriorates with time and may cause damage to the well; the space on the rig floor is limited, thus limiting the ability to conduct simultaneous operations such as drilling and picking up tubulars from the deck; and there are safety risks associated with a crane interface with the rig floor. All of the previous systems have only been able to pick up a single length of drill pipe, which is generally 30 feet long, or a single length of casing, which is generally 40 feet long.
Ideally, one would like to have a horizontal to vertical tubular transfer system that allows multiple segments of tubulars to be assembled on the deck, prior to being moved to the rig floor, then stored in a pipe rack until needed by the drilling operation. The system should minimize required manual contact with tubulars while maintaining the simplicity of the drilling operation. The tubular transfer system should also be relatively lightweight, and low-cost. The system should also increase the efficiency of the tubular handling operation.
The present invention is a method and apparatus for transferring tubular stands, which include more than one length of connected tubulars, between a substantially horizontal position on the catwalk and a substantially vertical position at the rig floor entry. In one embodiment of the invention, the drilling rig is a cantilever jack-up in which the cantilever beams are of sufficient length that three joints of Range II drill pipe (nominal 30 ft lengths) can be stored when assembled together; such a length of three drill pipes is normally called a stand. In this embodiment, individual joints of drill pipe are transferred from the main deck pipe racks to the cantilever pipe rack and then to a stand make-up/break-out machine, also called a bucking machine. The bucking machine stabs the drill pipe connections and makes them up to the correct torque. The drill pipe stand is then transferred from the bucking machine to a stand storage area (pipe rack) or to a trolley pick-up area. When additional stands are needed by the drilling operation, a trolley is moved into position over the trolley pick-up area to retrieve stands previously made up. The stands are clamped to the trolley and the trolley is moved from a substantially horizontal position to a substantially vertical position at the rig floor entry. A vertical pipe racking machine permanently located in the derrick transfers the stands to the well center where it can be picked up by the traveling equipment or to the vertical pipe rack in the derrick (or set back) where it can be stored until needed by the drilling operation. The stand is made up to the drill string already in the hole and the stand is run into the hole. This operation is repeated until all of the drill pipe required by the drilling operation has been installed in the hole. The operation can also be reversed to remove stands from the rig floor entry and break out the stands in a horizontal position on the cantilever pipe rack deck. The description above relates to drill pipe but exactly the same process can be applied to casing, which normally comes in 40 ft lengths and therefore a stand of casing in this embodiment will consist of two joints of pipe also made up by the bucking machine on the cantilever pipe rack deck.